The U.S. Air Force has long monopolized the job of controlling combat aircraft in support of army ground troops. Until about two decades ago, all of these "air controllers" (or FACs, for "Forward Air Controller") were pilots. But it was always a problem getting sufficient pilots to volunteer for this duty, and the training for the job was taking longer and longer. Moreover, in the late 1970s, the air force began assigning air controllers directly to specific army combat units. In the past, the controllers lived at an air base, only joining with an army unit for training or actual operations. This often created problems, as the army troops were leery about working with a bunch of "strangers." With air control parties (the officer who called in the air strikes and several enlisted airmen to help with the equipment) assigned to army units, more air force personnel were needed for this duty. So in the early 1980s, a new job category, terminal air controllers, was established and staffed with sergeants.
Currently there are 980 enlisted terminal air controllers and 350 officer combat controllers. These 1300 air force personnel are something of an elite force. Most have gone to jump school, and taken much army combat training (including, for some, sniper school). They serve full time with the army units they support, distinguished in the field only by their unique air force rank badges (for the enlisted troops only, as air force and army officers use identical rank insignia.) The air force personnel are considered combat qualified, and in Afghanistan and Iraq many of them found themselves using their M-16s against nearby threats, as well as calling in bombs from overhead warplanes. In fact, fighter pilots serving as controllers on the ground suffer a much higher casualty rate than then their brethren who are still flying. This was even the case in Vietnam, where seven percent of the 3,000 air force controllers were killed in action.
In Afghanistan, the air force had plenty of controllers, so much so that they were able to keep out navy ground controllers (who also handle gun fire support from warships, which was not an issue in landlocked Afghanistan.) The navy was not happy with this, but the air force did have the situation covered. Iraq was a different story, and there were shortages, even with the navy controllers present. At this point, the army and the marines realized several things. One, the GPS smart bombs made bombing missions close to the troops much more popular. Combat commanders now wanted someone in each platoon to call in air strikes. Second, the equipment needed to call in air strikes was lighter, there was less of it and it was easier to use. Third, the air force sergeants who were doing most of the controller work were very, very good. The conclusion was that the army and marines wanted to train some of their own NCOs for these tasks. They had seen how the air force did it (two years of on-the-job training as an assistant to an enlisted controller, then months of formal training), and knew they had people who could do it as well.
The air force is cooperating in the training of army and marine sergeants and officers to be controllers, and doesn't see it's own controllers going away. The air force officer controllers, who command the enlisted controllers and take care of larger issues (like arranging for air dropped troops or supplies and the use of improvised air fields during combat, and so on) are always going to be needed. The air force NCO controllers are another matter. When the air force began training sergeants to be controllers, they found there were many young air force NCOs who wanted that kind of job. There are always far more volunteers than there are open positions for new terminal air controllers. But it would cost the air force over a hundred million dollars a year to supply as many controllers as the army and marines now want. But the air force may be able to save some money if they help train army and marine NCOs to be controllers, and maybe even cut back on the number of air force NCOs doing this work.